The invention relates to the technical field of mandibular advancement orthoses. Different solutions have been proposed for causing the mandible to move relative to the maxilla.
The required aim is to move the mandible forward relative to its original position by a very small distance of the order of a few millimeters, initially, in order, in particular, to stimulate growth. This mandibular propulsion may be used to increase respiratory flow, in order to sort out sleep apnoea syndrome problems.
The invention relates more particularly to an orthodontic assembly of the type perfectly understood by those skilled in the art and known as a “Herbst orthosis” or “Herbst rods”.
Essentially, this type of orthosis has splints engaging with the row of top teeth and the row of bottom teeth, respectively. These splints are generally made out of a rigid material, for example thermo-formed acrylic resin, and are connected to each other by a system of rods mounted with sliding capability. To be more precise, two metal rods are arranged, respectively, on each side of a reinforcement made interdependent with a part of the upper splint and lower splint. The two rods are connected with articulation capability on the reinforcement, substantially at primary molar level in respect of the upper splint and substantially at canine level in respect of the lower splint. The rods, on the corresponding reinforcement parts, as previously indicated, are articulated by means of an axis arranged in a substantially horizontal plane, such that the articulation movement of the rods is restricted in a vertical plane.
This restricted movement of the mandible relative to the maxilla, in a postero-anterior direction, is not satisfactory. It has proved important, for patients fitted with this type of orthodontic assembly, to be able also to have a high level of freedom of lateral movement of the mandible relative to the maxilla. It has also been noted that this type of horizontal axis articulation is cumbersome and makes it tricky to engage the rods of the upper and lower splints.
Systems for the articulation of an orthopaedic assembly are also known wherein the rods are coupled with the upper and lower splints, by means of a ball joint. The teaching in U.S. Pat. No. 5,620,321 may, for example, be cited. However, the solution described in this patent is not totally satisfactory given that it is not possible to obtain laterality movements.
The aim of the invention has been to overcome these drawbacks in a straightforward, safe, effective and rational manner.
The problem the invention sets out to resolve is how to confer total freedom of articulation of the rods both in an antero-posterior plane and in a lateral plane, and to do so while occupying less space.